1. Field of the Invention
This invention relates to display case doors and more specifically to commercial refrigerator display case doors, such as those used in grocery stores, convenience stores, and other grocery and product display environments.
2. Related Art
Conventional commercial refrigerator doors serve multiple functions. For example, the doors preferably provide a maximum viewing area for customers to view product. The doors also permit customers to open them to select and retrieve desired product from the display. The doors also seal the openings in the display cabinet to minimize the possibility of energy loss, while still preferably providing a low-profile, and a maximum viewing area. The door is preferably sufficiently strong and relatively rigid to withstand the impacts and effects of heavy use, such as any twisting, torquing, and other effects of constant opening and closing. The door also preferably includes a glass unit for providing the viewing area along with a suitable frame for protecting the glass unit from the effects of impact, and for mounting various hardware such as a handle, hinge mechanisms, and a door hold-open. A refrigerator door may also include heater wires for keeping the door frame relatively warm, compared to the cold compartment, to minimize the possibility of condensation forming on the frame.
Conventional refrigerator doors have achieved the appearance of maximum viewing area by providing an all-glass front. For example, the front and rear panels of glass can sandwich all or part of the door frame so that the forward panel is fully exposed, and not covered by any part of the door frame. In this design, the frame is at least partly internal to the glass unit and is covered for esthetic and protection purposes by a plastic shroud or cover. However, the additional components beyond a simple door frame typically add cost and manufacturing time for the door.
Other approaches to an all-glass front door include molding a frame around a glass unit, while leaving the forward glass panel exposed. Molding a door including set up time is also a time-intensive process and requires significant attention to insure proper positioning of the frame prior to molding.
A door is provided which reduces the time, space and labor necessary for assembling a door and which is easy to manufacture. The door also provides better thermal characteristics as well as an improved appearance.
An improved display door is provided with a glass unit and a spacer element extending between the panels of the glass unit. The door also includes at least one door rail element extending between the panels and also externally of the panels to form a perimeter wall for the door. This design provides easier manufacture, shorter manufacturing time, and reduced space requirements for assembly.
In one preferred embodiment, the door is formed with door rail elements made of a composite of fiber glass or other glass mats and rovings embedded in a thermoplastic resin. With the door rail element or elements formed from a composite material, the number of required parts can be significantly reduced, and the thermal characteristics of the resulting door are substantially improved. Moreover, in some environments, the conventional heating of the door frame to reduce or minimize vapor condensation can be entirely eliminated. The door rail elements can be efficiently manufactured by producing the rail elements as lineal sections followed by routing or other processing in order to make the door rail elements suitable for assembly with a glass unit as a door.
In a further form of the invention, door rail elements can be formed of a composite material having hollow frame elements extending between spaced apart glass panels. The hollow frame element not only provides support for the glass panels but also provides insulation in the form of an air pocket reducing heat transfer between the spaced apart glass panels. The composite rail element may also have a cover portion or flange portion that extends inwardly over a rearwardly facing portion of a rear most glass panel. The flange portion may include an arrangement such as a groove for accepting a sealing gasket. The flange may also be formed so as to include an air pocket between the rearward most glass panel and the flange portion to provide enhanced thermal insulation between the cold portion of the door and the outside environment.
In other embodiments, the frame portion extending between the glass panels includes projections for engaging sealant inserted between the glass panels for sealing the glass unit and for fixing the frame elements relative to the glass unit. Those projections preferrably includes circumferential ridges or other discontinuities for engaging the sealant.
An improved method of constructing or assembling a display door includes the steps of assembling a glass unit with two or more glass panels and spacer bars separating the glass panels. Pairs of rail elements are joined with corner keys and sealant is applied around the spacers and between the glass panels to seal the glass unit and to provide an anchor for the frame. Sealant is also preferrably placed in a groove in the frame elements into which the edge of the rearward most glass panel will be inserted. Two pairs of frame elements are then brought together and assembled with respective corner keys about the glass unit to set up the door. Where the door is a rectangular door, a band or a clamp can be placed around the center of the long dimension of the door, but such clamping or binding is not believed to be necessary, especially where the frame elements are formed from a composite material such as fiber glass embedded thermoplastic.
In a preferred embodiment, the door rail elements include perimeter wall elements which extend forward no further than the forward facing surface of the forward glass panel, to provide an all-glass front appearance. Preferrably, a cushion or tip extends between the perimeter edge of the forward glass panel and the adjacent perimeter wall portion so that the cushion can help to register or properly position the frame elements around the forward glass panel. Proper registration ensures alignment between the frame elements and the glass panel and proper appearance. Additionally, applying sealant to the groove for the rearward most glass panel allows adjustment for variations in glass shape or size in the rearward most glass panel. Therefore, upon assembly, the sealant and the spacing in the groove can easily accommodate variations in the rear glass panel while still permitting proper registration and fit between the forward glass panel and the door rail elements.
These and other benefits of the invention will become apparent upon consideration of the drawings, a brief description of which follows, and the detailed description of the preferred embodiments following.